Nearly ever basic biological process in humans and in vertebrates in general can be studied to great advantage in the fruit fly Drosophila. Olfaction is no exception. I wish to employ the genetic and in vivo physiological tools that are available for Drosophila to study the development of the olfactory system, in particular, how each olfactory sensory neuron acquires its final differentiated form. I will study the POU-domain transcription factor encoded by acj6, which is required in many neurons for their sensitivities to specific subsets of odorants. I will screen for new genes which interact with acj6, focusing on mutations which are likely to be in transcriptional target genes of the Acj6 protein, or in genes encoding proteins that interact with Acj6. In parallel, I will investigate the hypothesis that three other Drosophila POU genes also play a role in olfaction, by examining the expression of these genes in the olfactory organs, and by performing electrophysiological tests on mutants for these genes.